Until now, carbon capture developments have focused mainly on removing greenhouse gases at their source, such as the emissions of power plants, refineries, concrete plants and other industries.
However, University of Cincinnati Professor Joo-Youp Lee said the Golden Fleece of carbon capture draws carbon dioxide directly from the atmosphere, which is much harder.
“The concentrations of carbon dioxide in the atmosphere are so low,” he said. “It would be like trying to remove a handful of red ping-pong balls from a football stadium full of white ones.”
He is a professor of chemical engineering at UC’s College of Engineering and Applied Science. But Lee and his students have developed a promising system of removing carbon dioxide at about 420 parts per million from the air. And with his process called direct air capture, it can be deployed virtually anywhere.
Power plants and transportation generate about 53 per cent of all carbon dioxide emissions. Industry, commercial and residential buildings, agriculture, and other human activities generate the remaining emissions.
“Although industrial decarbonization efforts are underway, it’s tough to implement carbon capture in the remaining sectors,” Lee said.
Lee’s lab system uses electricity to separate carbon dioxide. However, he is advancing it by using hot water instead of electricity or steam, making it more energy-efficient than other carbon-capture systems. The system is also robust enough to last for thousands of cycles.
Lee built a benchtop model about the length of a pool noodle to test his system. Air from outside the building is pumped through a canister. Lee said they can’t use indoor air because it typically contains more carbon dioxide from the people using the building.
Inside the canister, the air whooshes through a honeycomb-like block wrapped with carbon fibre that Lee’s lab had custom-manufactured. The individual cells of the block are coated with a special adsorbent material that Lee’s team designed to capture carbon dioxide. Gauges on the air intake and exit measure the amount of carbon dioxide in the air. When the readings on the block outlet begin to climb, Lee’s students know it’s time to heat the structure to remove the trapped carbon dioxide with a vacuum pump and begin the process again.
UC researchers have been able to repeat the process more than 2,000 times without seeing any decline in efficiency or degradation of the materials. But Lee said he thinks 10,000 cycles is within reach. This efficiency would make the system more economically appealing.
Lee’s team scaled up the project in one of UC’s high-bay engineering labs, where students work on engines and other large industrial projects. Here, Lee maintains a climate-controlled environmental chamber where he can perform larger-scale experiments with his concept.
They built a person-sized canister that again draws air from outside the building. However, this sealed room allows them to control temperature, humidity, and wind speed. They also use larger honeycomb blocks the size of a loaf of bread.
“I think it’s a great project. We’re doing some real applications that can help the environment,” UC postdoctoral fellow Soumitra Payra said.
Payra is optimistic that this technology will be pulling carbon dioxide out of the atmosphere at scale soon.
Lee hopes the U.S. Department of Energy will continue to support his plans to develop an industrial-size prototype based on the promise of his demonstration system.
“Our technology has proven to reduce the heat required for the desorption by 50%. That’s a huge improvement,” he said. “By using half of the energy, we can separate carbon dioxide more efficiently. And we can make the cycle longer and longer.”
Projects like this could be funded through carbon credit systems, such as the Regional Greenhouse Gas Initiative, which indirectly funds energy efficiency programs in 11 states.
Lee said these systems could be instrumental in addressing climate change as demand for electricity is expected to surge in years to come.
“Big tech companies like Google, Microsoft and Amazon are supporting this type of research. They will need a lot of energy to run their data centres,” he said. “In the carbon tax credit market, the more electricity you use, the more carbon dioxide you emit. So they’re buying carbon tax credits, which support the development of these carbon-capture technologies.”
Lee’s research is supported through the U.S. Department of Energy National Energy Technology Laboratory.
“I’m pretty proud of the progress of our technology development,” he said.
